In general, a compressor converts a mechanical energy into a compression energy of a compressible fluid, and can be generally divided into a reciprocal type, a scroll type, a centrifugal type and a vane type.
A rotary compressor is typically applied to an air conditioner. As functions of the air conditioner are diversified these days, a rotary compressor capable of varying capacity has been demanded. For this, a method by which compressor capacity is varied by controlling the rotation numbers of the compressor is known. However, this method requires for a complicated controller to thereby increase the product price. A capacity varying unit that is cheap and stable needs to be provided. The present invention relates to this.
FIG. 1 is a twin rotary compressor in accordance with a conventional art, FIG. 2 is a block diagram for varying capacity in a conventional capacity variable type twin rotary compressor, and FIGS. 3 to 6 are plan views a change of a vane according to each driving in the conventional capacity variable type twin rotary compressor.
As shown therein, the conventional twin rotary compressor includes as illustrated in FIG. 1: a casing 1 installing a gas intake pipe (SP) and a gas discharge pipe (DP) such that the gas intake pipe (SP) and the gas discharge pipe (DP) communicate with each other; a motor unit 2 comprising a stator 2a and a rotor 2b installed at an upper side of the casing 1 so as to generate a rotating force; and a first compression unit 10 and a second compression unit 20 vertically installed at a lower side of the casing 1, receiving a rotating force being generated from the motor unit 2 by a rotating shaft 3 and individually compressing refrigerant.
As illustrated in FIG. 2, one accumulator 4 for separating liquid refrigerant from intake refrigerant is installed between the gas intake pipe (SP) and each of the compression units 10 and 20. A refrigerant switching valve 5, which is a three-way valve, switching the refrigerant and supplying the refrigerant to the second compression unit is installed between an outlet of the accumulator 4 and the gas discharge pipe (DP).
In addition, the nutlet of the accumulator 4 is connected with an intake 11a of a first cylinder 11 and an intake-side inlet 5a of the refrigerant switching valve 5, a bypass pipe 32 diverges from the gas discharge pipe (DP) and is connected with a discharge-side inlet 5b of the refrigerant switching valve 5, and an outlet 5c of the intake side of the refrigerant switching valve 5 is connected to an intake side of the second compression unit 20, all of which are described later.
As illustrated in FIGS. 1 and 2, the first compression unit 10 includes: the first cylinder 11 having an annular shape and installed inside the casing 1; a main bearing 12 and a middle bearing 13 covering both upper and lower sides of the first cylinder 11, forming a first inner space (V1) and radially supporting the rotating shaft; a first rolling piston 14 rotatably coupled with an upper eccentric part of the rotating shaft 3 and compressing the refrigerant, orbiting in the first inner space (V1) of the first cylinder 11; a first vane (not illustrated) movably coupled with the first cylinder 11 in a radial direction so as to pressingly contact to an outer circumferential surface of the first rolling piston 14 and dividing the first inner space (V1) of the first cylinder 11 into a first intake chamber and a first compression chamber; and a first discharge valve 15 openably coupled to a front end of a first discharge port 12a formed in the vicinity of the center of the main bearing 12 so as to control the discharge of the refrigerant being discharged from the first compression chamber.
The first cylinder 11 forms a first vane slit (not illustrated) reciprocating in the radial direction by inserting the first vane (not illustrated) into one side of an inner circumferential surface forming the first inner space (V1), forms the first intake 11a communicating with the outlet of the accumulator 4 and inducing intake refrigerant at one side of the first vane slit, and forms a first discharge groove 11b discharging refrigerant gas being discharged from the first compression chamber into the casing I at the other side of the first vane slit.
As illustrated in FIGS. 1 to 3, the second compression unit 20 includes: a second cylinder 21 having an annular shape and installed under the first cylinder 11 inside the casing 1; a middle bearing 13 and a sub-bearing 22 covering both upper and lower sides of the second cylinder 21, forming a second inner space (V2), and supporting the rotating shaft 3 in a radial direction and in an axial direction; a second rolling piston 23 rotatably coupled with a lower eccentric part of the rotating shaft 3 and compressing the refrigerant, orbiting in the second inner space (V2) of the second cylinder 21; a second vane (illustrated in FIG. 3) 24 movably coupled with the second cylinder 21 in the radial direction so as to pressingly contact to an outer circumferential surface of the second rolling piston 23 and dividing the second inner space (V2) of the second cylinder 21 into a second intake chamber and a second compression chamber; and a second discharge valve 25 openably coupled with a front end of a second discharge port 22a formed in the vicinity of the center of the sub-bearing 22 and controlling the discharge of the refrigerant gas being discharged from the second chamber.
The second cylinder 21 forms a second vane slit 21a at one side of an inner circumferential surface forming the second inner space (V2) such that the second vane 24 reciprocates in the radial direction, forms a second intake 21b at one side of the second vane slit 21a such that intake refrigerant or discharge refrigerant flows in by connecting a second refrigerant guide pipe 33 with the outlet 5c of the intake side of the refrigerant switching valve 5, and forms a second discharge groove 21c discharging refrigerant being discharged from the second compression chamber into the casing 1 at the other side of the second vane slit 21a. 
An expansion groove communicating with the inside of the casing 1 is formed at a rear end of the second vane slit 21a such that the rear side of the second vane 24 is affected by internal pressure of the casing 1, and a permanent magnet 26 is installed at expansion groove 21d so as to attract the second vane 24. Undescribed numeral reference 31 denotes a first refrigerant guide pipe.
The driving of the conventional twin rotary compressor will be described.
That is, when power is supplied to the stator 2a of the motor unit 2 to thereby rotate the rotor 2b, the rotating shaft 3 rotates together with the rotor 2b and transfers a rotary force of the motor unit 2 to the first compression unit 10 and the second compression unit 20. The first compression unit 10 and the second compression unit 20 perform power driving to thereby generate large-capacity cooling capability or only the first compression unit 10 performs power driving and the second compression unit performs saving driving to thereby generate small capacity cooling capability.
Here, each driving with respect to the second compression unit of the twin rotary compressor will be described in detail.
First, in a starting state as illustrated in FIG. 3, by communicating the inlet 5a and the outlet 5c of the intake side of the refrigerant switching valve 5 with each other, refrigerant gas of balance pressure is drawn into the second inner space (V2) of the second cylinder 21 through the second intake 21b . As pressure inside the casing 1 still maintains balance pressure (Pb), pressure (PB) of the refrigerant gas pushing the rear end of the second vane 24 and compression chamber pressure (Pb) of the second inner space (V2) maintains an approximate balance state.
Accordingly, the second vane 24 is attracted by a magnetic force of the permanent magnet 26, moves outside of the second vane slit 21a, and is separated from the second rolling piston 23, so that compression does not occur. In this state, the so-called vane jumping phenomenon that internal pressure of the casing 1 increases so that the second vane 24 is separated from the permanent magnet 26, comes in contact with the second rolling piston 23 and is attached to the permanent magnet 26 again repetitively occurs.
Next, as illustrated in FIG. 4, in a power state, as the driving continues in the above-described starting state, pressure inside the casing 1 increases to discharge pressure (Pd), while pressure of the refrigerant gas drawn into the second inner space (V2) decreases to intake pressure (Ps).
Accordingly, as rear-side pressure of the second vane 24 considerably increases in comparison to front-side pressure, the second vane 24 is separated from the permanent magnet 26 and pressingly contacts with the second rolling piston 23 so that compression of the refrigerant gas gets started.
Next, in a saving state as illustrated in FIG. 5, as the refrigerant switching valve 5 drives to communicate the discharge-side inlet 5b and the intake-side outlet 5c communicate with each other, part of the refrigerant gas of the discharge pressure (Pd) flows in the second inner pace (V2) of the second cylinder 21. Here, as internal pressure of the casing 1 still maintains a discharge pressure (Pd) state, the rear-side pressure and the front-side pressure of the second vane 24 becomes in a balanced state. By a magnetic force, the second vane 24 moves to the rear side where the permanent magnet 26 exists and is separated from the second rolling piston 23. As a result, compression does not occur in the second cylinder 21.
Meanwhile, when a driving state is changed, for example, as illustrated in FIG. 5, when the second compression unit 20 is changed from the saving state to the power state, at the moment when pressure of the refrigerant flowing in the second intake 21b is changed into the intake pressure (Ps) from the discharge pressure (Pd), contact between the second vane 24 and the second rolling piston 23 becomes unstable and the vane jumping phenomenon occurs again. That is, the pressure of when the intake-side inlet 5a and the intake-side outlet 5c in the refrigerant switching valve 5 communicate with each other is less reduced than the discharge pressure (Pd) and becomes middle pressure (Pd+a). On the other hand, as pressure inside the casing 1 still maintains the discharge pressure (Pd), a force by differential pressure is greater than that by a magnetic force of the permanent magnet 26. Thus, the second vane 24 overcomes the magnetic force and comes in contact with the second rolling piston 23 to divide the second inner space (V2) into a compression chamber and an intake chamber, such that compression is performed in the second inner space (V2) of the second cylinder. However, when the compression chamber pressure of the second inner space (V2) reaches the discharge pressure (Pd) again, the force by the differential pressure becomes greater than the magnetic force. As the second vane 25 is retracted by the permanent magnet 26 and is separated from the second rolling piston 23, compression does not occur and the driving state is changed into the power state.
However, in the conventional capacity variable type twin rotary compressor, as the so-called vane jumping phenomenon that the second vane 24 is detached from the second rolling piston 23 by a disproportion between differential pressure and a magnetic force when the compressor starts or its driving is switched occurs, noises of the compressor are increased. In addition, in order to reduce compressor noises in consideration of this during the starting, the starting must be performed when the second vane 24 is completely separated from the second rolling piston 23, that is, only in a saving mode.
In addition, in the conventional capacity variable type twin rotary compressor, as the second compression unit 20 performs variable driving, while the first compression unit 10 always performs normal driving, it is constructed to perform two-step capacity variable driving, which causes a limit to various control of functions of the air conditioner and deteriorates energy efficiency by generating cooling capability more than necessary and increasing unnecessary power consumption.